Something weird just happened. We had 3 lights on, 2 on smart plugs and 1 on a switch. All 3 just blinked off and back on. First thought was power blip but nothing else in house was affected, which usually happens on power blip.
Looked at my light dashboard and it showed all my lights on, but only the original 3 were actually on. Logs showed a connection error to Alexa and Google home and my Genie garage door opener.
Would those errors cause what I saw?
Do you have hunches turned on in alexa? Check your alexa app..Turn off hunches.
Hunches not and have never been turned on.
Which wireless system's being used to control the smart devices?
Possibly a red herring, but we've seen similar behaviour at my mum's house (not Hubitat'ed, but with a few TP-Link WiFi plugs); all controlled devices blink off for a second or so, then back on, at the same time.
(Unfortunately even if it is WiFi for you we never actually worked out the cause of this, but have speculated it was down to the house internet connection and/or the TP-Link servers having a bad day. That fits with your Alexa/Google Home errors.)
Plugs were Zigbee, light switch is Z-wave.
It's no biggy, but sure wondering what might have happened. Especially after the fact all my lights, both Zigbee and Z-wave were showing on when they wern't. Almost like the hub itself blinked. It is on a UPS, so power shouldn't have been an issue. And the TV was on and it didn't blink. The microwave clock which seems to be the most sensitive was fine also.
Take a look at the bottom of the Device page for your devices, You'll see an "In Use By" section:
Check to ensure there isn't an app using the devices that may have caused a blip...unlikely, but worth a quick look.
I had a similar problem w/a switch a while back, and finally figured out I had two competing automations where one was turning on the switch and another was turning it off immediately. Probably not your case unless you very recently made some changes to your automations.
Other than that, you may need to call her in to "clean your house:" 
Checked all that. Other than Alexa control on one of them it isn't even in any automations. Just manual, or voice, activated on/off.
Another thing that kinda rules that out is all the other lights suddenly reporting on when they aren't.
I'm thinking it was some sort of blip in the Echo system as all of the devices are linked to Echo. Maybe Alexa got bored and told everything to come on but realized it was wrong and immediately told everything to go off or something..
IRRC Alexa turns on Hunches w/out asking so that would have been my first guess along w/@rlithgow1, but you already checked that.
Alexa/Echo does still seem like the most likely culprit. Their evil is subtle and powerful.
This happened to me a few days ago. No reason could be found. I ended up assuming a brief Hue glitch - or maybe it was updating the bridge (all my lights are on the Hue system exposed to Hubitat)
Download the Hubitat app
